National Clinical Research Center for Respiratory Diseases, China-Japan Friendship Hospital, Capital Medical University, Beijing, China.
Laboratory of Clinical Microbiology and Infectious Diseases, Department of Pulmonary and Critical Care Medicine, Center for Respiratory Diseases, China-Japan Friendship Hospital, Beijing, China.
BMC Microbiol. 2021 Aug 19;21(1):230. doi: 10.1186/s12866-021-02293-0.
Resistance to ceftazidime-avibactam was reported, and it is important to investigate the mechanisms of ceftazidime/avibactam resistance in K. pneumoniae with mutations in bla.
We report the mutated bla is not the only mechanism related to CZA resistance, and investigate the role of outer porin defects, efflux pump, and relative gene expression and copy number of bla and ompk35/36. Four ceftazidime/avibactam-sensitive isolates detected wild type bla, while 4 ceftazidime/avibactam-resistant isolates detected mutated bla (bla, bla, and bla). Compared with other ceftazidime/avibactam-resistant isolates with the minimal inhibitory concentration of ceftazidime/avibactam ranging 128-256 mg/L, the relative gene expression and copy number of bla was increased in the isolate which carried bla and also showed the highest minimal inhibitory concentration of ceftazidime/avibactam at 2048 mg/L. The truncated Ompk35 contributes rare to ceftazidime/avibactam resistance in our isolates. No significant difference in minimal inhibitory concentration of ceftazidime/avibactam was observed after the addition of PABN.
Increased gene expression and copy number of mutated bla can cause high-level ceftazidime/avibactam resistance.
已有报道称对头孢他啶-阿维巴坦产生耐药，因此有必要研究肺炎克雷伯菌中 bla 基因突变与头孢他啶/阿维巴坦耐药的相关机制。
我们报告称 bla 的突变并非唯一与 CZA 耐药相关的机制，并研究了外孔蛋白缺陷、外排泵以及 bla 和 ompk35/36 的相对基因表达和拷贝数的作用。4 株头孢他啶/阿维巴坦敏感分离株检测到 bla 为野生型，而 4 株头孢他啶/阿维巴坦耐药分离株检测到 bla 发生突变（bla、bla 和 bla）。与其他头孢他啶/阿维巴坦耐药分离株（头孢他啶/阿维巴坦的最小抑菌浓度范围为 128-256 mg/L）相比，携带 bla 的分离株的 bla 相对基因表达和拷贝数增加，且其头孢他啶/阿维巴坦的最小抑菌浓度最高，达到 2048 mg/L。在我们的分离株中，截短的 Ompk35 对头孢他啶/阿维巴坦耐药的贡献很少。加入 PABN 后，头孢他啶/阿维巴坦的最小抑菌浓度没有显著差异。
突变 bla 的基因表达和拷贝数增加可导致高水平的头孢他啶/阿维巴坦耐药。
